The present disclosure relates generally to the field of automated maintenance (including nondestructive inspection) of aircraft structural elements such as airfoil-shaped bodies, and more particularly to an automated end effector-carrying apparatus that is coupled to and travels along an airfoil-shaped body having a relatively short chord length while performing a maintenance function.
U.S. patent application Ser. No. 13/663,709 discloses automated apparatus for performing maintenance functions on airfoil-shaped bodies having short chord lengths, without the necessity of removing the airfoil-shaped body from the aircraft. One such apparatus comprises a platform, an end effector carried by the platform, the end effector being selected from a group of interchangeable end effectors, means for mounting the end effector-carrying platform on an airfoil-shaped body, means for moving the end effector-carrying platform in a spanwise direction along the airfoil-shaped body, and means for moving the end effector in a chordwise direction relative to the airfoil-shaped body when the platform is stationary. In one implementation, the automated apparatus comprises a blade crawler which is movable in a spanwise direction and comprises a traveling element (e.g., a slider) that is linearly translatable in a chordwise direction when the spanwise-movable blade crawler is stationary. The selected end effector (mounted to the aforementioned slider) can be moved in a chordwise direction when the blade crawler is stationary. The foregoing blade crawler was designed to use the leading and trailing edge features of the blade to maintain its alignment with the blade. In practice, however, it can be difficult to maintain crawler alignment on complexly curved blades with twist, camber and sweep. In addition, a blade crawler should be able to traverse over trailing edge protrusions such as trim tabs, trim tab covers, and other irregularities.
Some proposed solutions are too complex, having too many components. For example, one proposed solution employed a multiplicity of alignment/follower wheels and a compression spring to induce crawler alignment using compression mechanisms. Further, an aft follower wheel was employed provide compression against the trailing edge. This creates a difficulty when the crawler encounters trailing edge protrusions (e.g. trim tabs) necessitating a host of complex mechanisms in order to accommodate these anomalies. Complex alignment systems of the foregoing type can be expensive to develop, manufacture and maintain. For example, the opposing compression mechanisms of the rollers and alignment wheels may require continuous fine tuning and adjusting. Unless the compressing forces are adjusted properly, the crawler may encounter misalignment, thus lowering the usage value of the apparatus.
Some current solutions are limited in their effectiveness in that they do not accommodate swept blade configurations well. A crawler that can accommodate only moderate contour complexities may require either significant kinematics re-programming or manual operator intervention. Next generation helicopter blades and emerging blade designs will have significant swept tip designs. This will be a significant difficulty that may need to be overcome for maintenance blade crawlers to be successfully deployed to factories, depots and forward bases.
A blade crawler design that improves the crawler's ability to navigate over swept helicopter blade configurations and simplifies the componentry that couples the crawler to the helicopter blade would be a technological advance.